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We present radial velocity follow-up obtained with ESPRESSO of the M-typestar LTT 1445A (TOI-455), for which a transiting planet b with an orbitalperiod of~5.4 days was detected by TESS. We report the discovery of a secondtransiting planet (LTT 1445A c) and a third non-transiting candidate planet(LTT 1445A d) with orbital periods of 3.12 and 24.30 days, respectively. Thehost star is the main component of a triple M-dwarf system at a distance of 6.9pc. We used 84 ESPRESSO high-resolution spectra to determine accurate masses of2.3$\pm$0.3 $\mathrm{M}_\oplus$ and 1.0$\pm$0.2 $\mathrm{M}_\oplus$ for planetsb and c and a minimum mass of 2.7$\pm$0.7 $\mathrm{M}_\oplus$ for planet d.  Based on its radius of 1.43$\pm0.09$ $\mathrm{R}_\oplus$ as derived from theTESS observations, LTT 1445A b has a lower density than the Earth and maytherefore hold a sizeable atmosphere, which makes it a prime target for theJames Webb Space Telescope. We used a Bayesian inference approach with thenested sampling algorithm and a set of models to test the robustness of theretrieved physical values of the system. There is a probability of 85$\%$ thatthe transit of planet c is grazing, which results in a retrieved radius withlarge uncertainties at 1.60$^{+0.67}_{-0.34}$ $\mathrm{R}_\oplus$. LTT 1445A dorbits the inner boundary of the habitable zone of its host star and could be aprime target for the James Webb Space Telescope.

Planetary system around LTT 1445A unveiled by ESPRESSO: Multiple planets in a triple M-dwarf system